The present invention relates to an image reading method for performing prescan under the optimum reading conditions in a case where images recorded on a film are read by consecutively prescanning the images at low resolution and, then, consecutively fine scanning the images at high resolution.
Heretofore, the images recorded on photographic films such as negatives and reversals (hereinafter called as film) have been commonly printed on light-sensitive materials (photographic paper) by means of direct exposure in which the film image is projected onto the light-sensitive material to achieve its areal exposure.
A new technology has recently been introduced and this is a digital print system that relies upon digital exposure. Briefly, the image information recorded on a film is read photoelectrically, converted to digital data and subjected to various image processing operations to expose the light-sensitive material digitally. The digital print system operating on this principle has been commercialized as the digital print system.
The digital print system is basically composed of: an image reading apparatus such as a scanner that photoelectrically reads the image data recorded on an original such as a transparent original, a reflection original or the like; an image processing apparatus that subjects an inputted image data to various processing operations, as well as controls and administers operations of the digital print system as a whole; and an image recording apparatus including a printer that exposes the light-sensitive material digitally in accordance with the image data subjected to those image processing operations, a processor which performs development on the exposed light-sensitive material and the like.
In the digital print system, the scanner reads an original image. The read image data is converted to digital data from which image processing conditions (exposure conditions)are determined in the image processing apparatus for allowing the image data to be subjected to various image processing steps. In the printer, the light-sensitive material is scan exposed in accordance with the image data subjected to image processing operations to form a latent image thereon and sent to the processor where development processing as determined by the light-sensitive material are performed to produce a finished print (photograph) reproducing the image that was recorded on the film.
The digital print system is capable of shortening a exposure time and therefore performing a quick exposure and, in addition, storing the image information of the finished print in a recording medium such as a photomagnetic disc or the like, so that, for example, it is unnecessary to read the film again and it is possible to facilitate and expedite an extra printing operation and the like. Moreover, the system has several advantages such that the system is capable of performing freely image processing including image editions such as image composites, image splits and the like, and other image processing such as color/density adjustment and the like to output the finished print subjected to editing and image processing in a free manner in accordance with applications.
When the film is read by the scanner, the film is first prescanned with a default reading condition so as to read the images recorded on the film at low resolution; secondly, a fine scan reading condition and image processing conditions are determined based on the thus prescanned images; thirdly, the film is fine scanned by the thus determined fine scan reading conditions to read images recorded on the film at high resolution; and lastly, the thus read fine scanned images are subjected to image processing operations under the above-described image processing conditions.
In a case that densities of base films differ from each other manufacturer by manufacturer as well as product by product, the default reading conditions of the film at prescanning are required to control a stop-down value (F-number) of a variable diaphragm or storage time of an image sensor so as to maintain a light quantity to be less than that which saturates the image sensor, even when the light passed through the brightest part (the minimum density part) of the film, for example, a negative base (base film) in the case of the negative film, is inputted into the image sensor.
However, densities of base films greatly differ from each other manufacturer by manufacturer as well as product by product so that setting the light quantity for prescan based on the base film with a low density will bring about a light quantity shortage when images recorded on the base film with a high density are read whereas setting the light quantity based on the base film with a high density will be liable to saturate the image sensor when images recorded on the base film with a low density are read.
Having these features, the ordinary digital print system is arranged to display messages such as xe2x80x9cfilm density is low.xe2x80x9d, if the image sensor is saturated when the film with a low density is prescanned. Accordingly, when such a warning message is displayed, an operator is required to reset the light quantity for prescan by a manual operation in accordance with film kind so as to prescan the film again. Such a manual operation is time- and labor-consuming to cause decrease of productivity.
In view of the above-described problems based on the prior art, the present invention has an object to provide an image reading method capable of prescanning a film under the optimum reading condition automatically without requiring operator""s attention.
In order to achieve the stated object, the invention provides an image reading method for consecutively prescanning a film at low resolution and, then, consecutively fine scanning the film at high resolution to read a plurality of images recorded in respective frames of said film, comprising the steps of:
performing a first scan on a part of said film or said film as a whole under a first reading condition;
calculating a minimum density or density distribution information of said film;
judging necessity for a second scan under a second reading condition different from said first reading condition on the basis of the thus calculated minimum density or density distribution information of said film;
determining said second reading conditions based on said minimum density or density distribution information of said film at the same time of the judging step or in response to a result of the judging step; and
performing prescan under said second reading condition when said judging step results in that said second scan is necessary.
It is preferable that said first reading condition is a default reading condition.
It is preferable that said determining step of said second reading condition is performed either at the same time of the judging step of the necessity for said second scan or only when the judging step results in that said second scan is necessary.
It is preferable that when the judging step results in that said second scan is not necessary, instead of performing the prescan under said second reading condition, scanning said film as a whole under said first reading condition substitutes said prescan.
It is preferable that when the judging step results in that said second scan is necessary, said prescan is performed such that said second scan is performed under said second reading condition on a part of said film or said film as a whole after said second reading condition are determined.
It is preferable when the judging step of the necessity for said second scan is made while said first scan is being performed and said judging step results in that said second scan is necessary, said prescan is performed such that said second scan is successively performed by changing said first reading condition to said second reading condition.
It is preferable that changing said first reading condition to said second reading condition is performed when a frame detection is performed frame by frame and a frame of interest is detected among frame.
It is preferable that when the judging step of the necessity for said second scan is made while said first scan is being performed and said judging step results in that said second scan is necessary, said prescan is performed such that said second scan is performed on all frames of said film under said second reading condition by changing said first reading condition to said second reading condition.
It is preferable that said first scan is performed from one end of said film along its length and wherein, after said first scan is completed, said second scan is performed from the other end of said film along its length.
It is preferable that said first scan is performed from one end of said film along its length and wherein said second scan is performed from one of two ends of said film which is reached earlier in time than the other one of the two ends to the other one.
It is preferable that a plurality of the second reading conditions are previously stored and then a reading condition with high frequency of occurrence among the plurality of the stored second reading conditions is utilized as said first reading condition.
The invention provides an image reading method for consecutively prescanning a film at low resolution and, then, consecutively fine scanning the film at high resolution to read a plurality of images recorded in respective frames of said film, comprising the steps of:
performing scan on said film under a first reading condition;
calculating a minimum density or density distribution information of said film;
determining a second reading condition based on the minimum density or density distribution information of said film; and
performing prescan on said film under said second reading condition.
It is preferable that said first reading condition is a default reading condition.
It is preferable that judgement on necessary for the prescan is made based on the minimum density or density distribution information of said film and wherein, when the judgement results in that the prescan is not necessary, said second reading condition is substituted for said first reading condition.
It is preferable that said second reading condition is determined while said film is being scanned under said first reading condition and, thereafter, said film is prescanned under said second reading condition by changing said first reading conditions to said second reading condition.
It is preferable that changing said first reading condition to said second reading condition is performed when a frame detection is performed frame by frame and a frame of interest is detected among frames.
It is preferable that when said second reading condition is determined while said film is being scanned under said first reading condition, the prescan is performed on all frames of said film under said second reading condition.
It is preferable that the scan of said film under said first reading condition is performed from one end of said film along its length and wherein the prescan of said film under said second reading condition is performed from the other end of said film along its length.
It is preferable that the scan of said film under said first reading condition is performed from one end of said film along its length and wherein the prescan of said film under said second reading conditions is performed from one of two ends of said film which is reached earlier in time than the other one of the two ends.
It is preferable that a plurality of the second reading conditions are previously stored and then a reading condition with high frequency of occurrence among the plurality of the stored second reading conditions is utilized as said first reading condition.